Electromagnetic apparatus.



F. P. POOLE.

ELECTROMAGNETIC APPARATUS.

APPLICMION min APR. In. 1917.

1,262,838. Patented Apr. 16,1913.

//1 Ven for. Frede/'fd' P /000/2 N UNITED STATES PATENT oEEIcE.

FREDERICK P. POOLE, OF LA GRANGE, ILLINOIS, ASSIGNOB TO WESTERN ELECTRICCOMPANY, INCORPORATED, F NEW YORK, N. Y., A CORPORATION OF NEW YORK.

ELECTROMAGNETIC APPARATUS.

' Specification of Letters Patent.

Patented Apr. 16, 19178.

Application led April 11, 1917'.v Serial No. 161,188.

Apparatus, of which the following is a full,

clear, concise,and exact description.

This invention relates to electromagnetic apparatus'and has for itsobject the production of an electromagnetic structure, in whichthe'energizing winding may be accurately located and positively securedinA definite relation to t'hevendA of its core.

` Generally `stated the invention relates to an electromagneticstructure` in which the energizing coil iswound as a solenoid on ahollow spool, whichspool is adapted to be slipped overa core; the coreis provided with a seating 'portion adapted to serve as an abutment oran adjustable spacer interposed between one end of the spool and thesaid seat.

The invention resides more particularly in providing in anelectromagnetic structure, means whereb the energizing winding may beaccurate y located and definitely secured on a core and in apredetermined relation to the end thereof wherein variations in thedimensions of the individual parts of the structure may be compensatedfor at the time the said parts are assembled as a finished product, andwhereby continuous production of linished structures having uniformcharacteristics and of uniform efliciency is assured.

The invention is of particular importance in its relation to telephonereceivers where it has been found as the result of an extendedinvestigation including a series of tests that the transmissioneiiciency is governed to a considerable extent by the relation betweenthe energizing winding and the end of the core, and that variations inthe length of the portion of the core extending beyond the winding willcause variations in the transmission efficiency.

It has also been found upon investigation that transmission efficiencyincreases as the `length of the core extension beyond the winding isreduced, and that the best results are obtained by locating the windingas near as possible to the end of the core.

A better understanding of the invention.

may be obtained by referring to the drawing forming a part of thisapplication, which shows the invention as employed .in the constructionof a, telephone receiver and in which:

Figure 1 is a side view, `in section, of the ma etic structure of atelephone receiver;

. ig'. 2 is a side view of an eleetromagnet of the receiver shown in.Fig. 1;

Fi 3 is an end view of the electromagnet shown in Fig. 2 and illustratesthe method used in retaining the winding spool on the core; and

4 is a detailed and side view of a portion ofthe rear end of theelectromagn-et of Fig. 2, showing the adjustable spacer introducedbetween the endof the spool and the seat, or abutment on the pole pieceor core. The receiver illustrated in Fig. 1 comprisesamong other thingsa horseshoe permanent magnet 1, provided with extended pole pieces 2 ofreduced cross section, a pair of magnetizin coils 3, an inclosin cup 4for the pole iece extensions 2 and the coils 3, and a diap ragm 5. Therim of cup 4 is adted to serve as a seat for the periphery of e saiddiaphragm 5.

The coils 3 are wound on .bobbins consisting of two Bauges 6 and 7,mounted on a tube 8, all composed of s itule insulatin material such asaper, ru b or fiber, an

in the preferred orm of bobbin one end of the tube is extended a shortistanee beyond the flange 6. The interna dimensions of tubes 8 are suchthat the tubes will slide over the ends of the pole iece extensions 2und make a snug lit. etallic washers 10 are used for the purpose ofretaining the .4

coils on the pole extensions and the openings position that the ends ofthe tubes 8 projectmg beyond the flanges 6 are brought into engagementwith the abutments 9, The washers l are then also slipped overl theforward ends of the pole piece extensions and pressed into engagementwith the iijn es 7 of the bobbins. Lugs 11, struck out o the bodportions of the washers, pro3ect slightly into the opening through thecentral portions thereof. These lu grip the sides ot the pole extensionsan hold the said washers in lace, which washers, 4in turn, hold the coi3 in place on the pole extensions.

The complete magnetic structure, except the diaphragm, is then insertedinto a suitable machine. and pressure is applied to the Washers 10, andthey am forced along the pole extensions until the ends of suchextensions extend a, predetermined distance beyond the said washers. Thepressure applied to the washers 10, in addition to forcing the Washersalong the pole extensions, also forces the bobbins with their fwindingsas a whole-alon the said pole extensions but inasmuch es t e tubes ofthe seid bobbin spool are of a suitable material such as paper, rubberor fiber, the portions oi the said tubes 8 extending beyond the flanges6 are compressed or crumpled, and as a result permit the coils to movealon the pole extensions -far enough 4to permit the coils to be locatedat the predetermined position K and at the same time serve the purposeof 3 an adjustable spacer between the flanges 6 of the bobbins 3, andthe abutments 9. The extended portions of the tubes 8 in theirengegement with abutments 9 also provide a.

i ver with a core, an abutment ineens for holding the bobbins inengagement with the washers 10.

As an alternative method of assembling the coils into the magneticstructure, and in accordance with this invention, the ends of the tubesB may be made iiush with the flanes 6., and separate elements in theshape of t e tubes S and of any suitable material, may be slipped overthe pole extensions prior to the placing of the bobbins thereon, and thesaid separate tube sections will serve as adjustable spaces when thepressure is applied to the washers 10 for the purpose of seating thecoils on the pole extensions in their predetermined positions.

What is claimed is:

1. In an electromugnet, the combination of a core, nn abutment. 'on saidcore, n bobbin adapted to sli over said core, a. retaining washer forsaid bobbn, and a yielding spacing element between said bobbin and saidabutment, whereby said bobbin is held in a position determined by saidretaining washer.

2. In an electromagnet, the combination formed on said core, a bobbinadapted to sliliover said core, a. retaining device for said obbinadapted to it over the said core and to engage therewithand a.compressible spacing element on said core between the abutment and oneend of said bobbin adapted to permit the bobbin to assume, underpressure, a predetermined position, and to maintain the said bobbin inseid redetermined position.

In witness w ereof, I hereunto subscribe my name this 2nd day of April,A. D. 1917.

FREDERICK P. POOLE.

